While roller clutch cages are increasingly being molded of plastic for cost and weight considerations, metal cages are still sometimes preferred. Metal cages are specified by clutch designers for use in high heat environments, and they do avoid the drawback of differential coefficients of thermal expansion that occurs when tight fitting, concentric control plastic cages are used between steel races. A typical conventional metal roller clutch cage is shown in FIGS. 1 and 2, and indicated generally at 10. Cage 10 consists of two annular side rails or end rings 12 and a plurality of circumferentially spaced metal cross bars 14. Tabs on cross bars 14 are received through small slots 16 in the end rings 12 and headed over at 18 to complete the cage structure. One structural limitation of cage 10 is that its rigidity is limited by the amount of area covered by the headed over cross bar portions 18. Rollers and springs, not illustrated, are then added to cage 10 to give a complete clutch unit that can be installed in one step between a pair of conventional clutch races.
In cage 10, the cross bars 14 provide mounts for the springs and rest surfaces for the rollers during shipping, but do not touch the confronting inner surfaces of both races and do nothing, therefore, to maintain the clutch races concentric or coaxial to one another. That function is served entirely by the end rings 12. The outer edges of the end rings 12 include circumferentially spaced reaction ears 20 that tie the cage 10 non turnably to the cam race, which, in this case, would be the outer race. Separating the reaction ears 20 are arcuate edge portions 22 which would abut cylindrical portions of the cam race when the cage 10 is installed. There is no relative rubbing, of course, between the cam race and the arcuate edge portions 22. The inner edges of the end rings 12 are bent over to form bearing flanges 24 which would conform closely to and pilot on the cylindrical pathway of the inner race. The abutment of the end ring arcuate edge portions 22 with the cam race and the piloting of the end ring flanges 24 on the pathway serve to keep the clutch races radially separated and in substantially coaxial relation. Radial loads between the races are well supported, since the end rings 12 are very strong in radial compression. This design presents a couple of drawbacks in terms of manufacturing and cost, however.
Since the outer surface of the flanges 24 will be piloting on the pathway of the inner race at very high speeds during clutch overrun, and will be subject, therefore, to a great deal of potential rubbing wear, it is practically necessary to clad flanges 24 with a metal layer, such as aluminum, that will cooperate with the lubricant better than the base steel. Therefore, the end rings 12 are stamped from a clad steel material, which is relatively quite costly. As a consequence, the entire inner surface of the end rings 12 is clad as well, unnecessarily, just to obtain the needed cladding of the flanges 24. Another drawback is that the tolerance or accuracy with which the races will be maintained in coaxial relation is necessarily limited by the accuracy with which the radial separation between end ring arcuate edges 22 and the outer surface of the flanges 24, best seen in FIG. 2, can be maintained. The arcuate edges 22 are produced by a cutting operation, which is quite accurate, with a tolerance of approximately 0.001 inches, plus or minus. The flanges 24, however, are produced in a bending operation, which is not as accurate as cutting, with a tolerance of approximately 0.0035 inches. Therefore, there is a total tolerance stack up of perhaps 0.0045 inches. While this is by no means an unworkable tolerance, it would be desirable, if possible, to reduce it, doubly so if that reduction could be had in a structure that provided equal or better rigidity and ease of manufacture. Even more desirable would be a reduction in the amount of clad steel material used, with a consequent significant reduction in cost.